Access a named parameter with string in ruby

Question

I'm pretty newbie in ruby and I'm not sure that the question be suitable, but this is my problem.

I have a function with unlimited string parameters. I want to know if all of them are in the http request. This is my code :

def http__params_exists *list
    list.each do |p|
        if params[:'#{p}'].nil?
            return false
        end
    end
    true
end

Take an example : I have a query with the "lat" parameter. The condition that I want to be execute is if params[:lat].nil?

I tried some tricks, but all failed. Thanks.

ps :An other question about ruby. I don't know exactly the kind of objects that symbols like :method_not_allowed (for example) are. I know that we can call a function naming some parameters, but this object is already defined somewhere, as if it was a public variable of the controller, but it doesn't seems to be.

Kulbir Saini · Accepted Answer · 2012-08-25 02:02:22Z

2

You need to use " instead of ' so that the variable is interpreted. Example

a = 'string'

:'#{a}'
==> :"\#{a}"

:"#{a}"
==> :string

:"#{a}" == :string
==> true

So, your code shall be

...
if params[:"#{p}"].nil?
  return false
end
...

This is an interesting link to learn more about Ruby symbols.

answered Aug 25, 2012 at 2:02

Kulbir Saini

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1 Comment

mu is too short Over a year ago

p.to_sym would be another option.

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